Electric capacitor



Oct. 5, 1948. R. a. FLOWERS ETAL 2,450,650

ELECTRIC CAPACITOR I Filed Dec. 13, 1945 HIGH FREQUENCY SOURCEDIELECTRIC CONSISTS OF LJQUID ESTER CONTAINING ONE RICINOLEIC ACID GROUPOR DERIVATIVE THEREOF.

Inventors: 9 Ralph G.FIower*s, Leola Wills Flowers,

Their Attorney.

Patented Oct 5, 1948 t v I r UNITED STATES PATENT OFFICE 2,450,650 1ELECTRIC caracrroa Ralph G. Flowers and Leola Wills Flowers, Pittsfleld,Masa, assignors to General Electric Company, a corporation or New YorkApplication December 13, 1945, Serial No. 634,699- 1 Claim. (Cl. 175-41)The present invention relates to electric caether acetyl rlcinoleate(ethyl carbitol acetyl pacitors which are adapted to operate in the highricinoleate), ethylene glycol monomethyl ether frequency field, that is,in the field of frequenpropionyl rlcinoleate (methyl cellosolvepropionyl cies at least as high as about 100 kilocycles and rlcinoleate)and ethylene glycol monobenzyl ether commonly as high as 1000kilocycles. Our inven- 5 acetyl rlcinoleate. An example of a monoestertion comprises new and improved dielectric mateof an acid which may beconsidered as being rials for use in such capacitors consisting ofliquid ricinoleic acid in which the double bond has been monoesters ofricinoleic acid and its derivatives, saturated with hydrogen is ethyll2-acetoxy including 12-hydroxy stearic acid and also the stearate,Other examples of esters of l2-hydroxy acyl derivatives of such acids.stearic acid suitable for high frequency dielectric Liquid esters ofacyl derivatives of ricinoleic purposes are ethylene glycol monoethylether acid, such for example as actyl and propionyl 12-acetoxy stearate,ethylene glycol monoethyl rlcinoleate monesters, are included among theether 12-propionoxy stearate, ethyl 12-propionoxy I capacitors.

preferred forms of dielectric materials which stearate, and ethyleneglycol monobenzyl ether embody our invention. 1b lz-acetoxy stearate.

The accompanying drawing illustrates conven- The alcohol component ofdielectric esters emtionally a type of electric capacitor containing abodying our invention may be aliphatic or aryldielectric materialembodying our-invention. aliphatic alcohols, for example, methyl, ethyl,

Although in the course of years of research and propyl, butyl alcohols,ethylene glycol monoethyl development a. number of efllcient liquiddielecether, diethylene glycol monomethyl ether, ethyltric materialshave been provided for operation ene glycol monoethyl, ether anddiethylene glycol in capacitors in the low frequency field, includingmonobenzyl ether. In general the alcohol when frequencies of the orderof: to 60 cycles, it has esterified with one 01' the acid groups aboveindibeen found that such dielectric-materials are not cated shouldresult in a normally liquid material. adapted for use in the highfrequency field. 25 Liquid monoesters of ricinoleic or hydroxy stearicWe have discovered that liquid monoesters, acid in which the hydrogen ofthe hydroxy group that is, esters containing only one ricinoleic acid isreplaced by an acyl group are adapted for the group or derivative,function effectively in high purposes of our invention. The chemicalfor? frequency capacitors with desirable capacity mula of estersincluded as dielectrics of our incharacteristic and low energy losses.Such matevention may be represented as: rials have been found to be lessactive chemically and less susceptible to contamination than dielec-CH3(C'H:) 5.CH-(OR)CH2CH= tric materials heretofore used in highfrequency CH(CH2)7COOR' A typ of Spaced Plate capacitor to wh h 111 thedouble bond being unsaturated or saturated invention is applicable isshown in vertical secwith hydrogen. R represents an acyl radicle or tionin the accompanyin rawi hydrogen and R represents an aliphatic or aryl-The capacitor here shown comprises a conaliphatic radiel tainer or tankI in which are i p j x ap Ethylene glycol monomethyl ether acetylricinarmature plates 2, 3 which are connected by 40 oleate (methylceliosolve acetyl ricinoleate) is an conductors 4. 5 to s i l terminals6, h oily material having at ,660 kilocycles a dielectric capac tor p ts 3 of the aw may cons s constant of 4.2, at 70 c. a power factor of.086 of aluminum, tinned copper or tinned copp r per cent and adielectric strength of 260 volts/mil alloy. The drawing is intended torepresent symusing a 50 mil gap at 650 kilocycles. At one bolicallycapacitor plates which may be stationary megacycle this material has apowerfactor of or relatively movable with respect to one another. .11per cent and at 3.5 megacycles a power factor The armature plates areimmersed in a norof'.21%. Ethylene glycol monomethyl ether promallyliquid dielectric material 8 which consists pionyl ricinoleate at 660kilocycles has a dielectric of a monoester of ricinoleic acid or of asuitable constant of 4.5 and a power factor of 0.09 per derivativethereof. Examples of esters of ricinocent.

leic acid suitable for dielectric purposes are ethyl- Other examples ofliquid dielectric materials ene glycol monomethyl ether rlcinoleate(methyl which are suitable for the high frequency field are celiosolverlcinoleate) ethylene glycol monothe following: methyl ether acetylrlcinoleate (methyl celiosolve Ethyl 12-acetoxy stearate has .12 percent power acetyl ricinoleate), diethylene glycol monoethyl 5 factor anddielectric constant of 3.9 at one megacycle. Its insulation resistanceat 25 C. is 1.38x10 ohms per centimeter.

Ethyl 12-propionoxy stearate has .105 per cent power factor anddielectric constant of 3.8 at one megacycle. Its insulation resistanceat 25 C. is 122x10 ohms per centimeter.

Ethylene glycol monoethyl ether lZ-acetoxy stearate has .095 per centpower factor and dielectric constant of 3.9 at one megacycle. Itsinsulation resistance is .93 at 10 ohms per centimeter at 25 C.

, Ethylene glycol monoethyl ether l2-propionoxy stearate has .17 percent power factor and dielectric constant of 4.0 at one megacycle. Itsinsulation resistance is .93 at 10 ohms per centimeter at 25 C.

Ethylene glycol monobenzyl ether IZ-acetoxy stearate, ethylene glycolmonobenzyl ether acetyl ricinoleate and ethylene glycol monobenzyl etherpropionyl ricinoleate also are examples of liquid dielectric materialssuitable for the high inquency field.

The resistivity and power factors of high frequency dielectric embodyingour invention remain substantially unchanged after long periods ofoperation at 100 C. as well as at lower temperatures, thereby indicatingthat such materials are not readily susceptible to contamination. It hasbeen found necessary heretofore to refine high frequency liquiddielectric until an extremely high resistivity is obtained and tomaintain such high state of purity in order to obtain satisfactoryservice as a dielectric element in capacitors. The materials embodied inour invention have given excellent service in capacitors when theresistivity is only a small fraction of that required for the presentliquid dielectrics. A resistivity of about 67x10 ohms/cm. has been foundto be satisfactory.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

An electric capacitor comprising the combination of a container, spacedcooperating armatures therein, and a dielectric material consisting ofethylene glycol monomethyl ether acetyl ricinoleate,

RALPH G. FLOWERS. LEOLA WILLS FLOWERS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS 25 Number Name Date 1,955,021 Rider Apr. 17, 1934FOREIGN PATENTS Number I Country Date 30 119,404 Australia Jan. 4, 1945

